Radiometric Dating Q&A

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Chaffey College *

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Anthropology

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Dec 6, 2023

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Radiometric Dating Q&A 1. What is the most common form of radiometric dating in geology and anthropology? Carbon-14 dating. 2. According to Slide #3, how old would a body be if it had only 30% of its original Carbon-14? 10,000-years-old. 3. What dating method is used on hominids as old as 3.2 million years, such as Lucy? Potassium-argon dating. 4. Since we can’t use the potassium-argon method directly on fossils, what substance do scientists use the potassium-argon method on? Layers of volcanic ash. 5. Looking at the table on Slide #5, what radiometric method is used for the youngest artifacts? Carbon-14 dating. 6. What radiometric method was used to date the 1.7 billion-year-old rocks in the San Gabriels? Uranium-lead dating. 7. Which mineral provides the best time capsule for radiometric dating? Zircon. 8. Slide #6 shows pictures of the typical San Gabriel rock called gneiss (pronounced as “nice”). How would you describe the appearance of gneiss? There are alternating dark and light colors where the minerals segregate into different layers. 9. Where is carbon enriched in the gully walls at Valyermo? In the peat layers. 10. What two pieces of information would Carbon-14 dating of the San Andreas fault provide? They determined how often the fault broke in the past and how much the ground moved. 11. What did geologists obtain at Baldwin Lake to study its ancient climates? They obtained a 27-meter core. 12. When did Big Bear and Baldwin Lakes likely have glaciers? 14,000 to 32,000 years ago. 13. In Slide #9, what three materials can be radiocarbon dated? Wood, bone, and carbonate materials.

The questions below are based on the Labster simulation. There are a lot of questions, but it will make the simulation much easier if we review the chemistry vocabulary. 14. What are the three critical ingredients of atoms? Protons, neutrons, and electrons. 15. What two particles reside inside the nucleus of an atom? Protons and neutrons. 16. How do they define a nuclide? A nucleus with a specific number of neutrons and protons is called a nuclide. 17. What causes a nuclide to break down? Adding or removing neutrons and protons to a stable nuclide can make it less stable. 18. What is the atomic number? Z, the atomic number, is the number of protons in a nuclide. 19. What is the mass number? A, the mass number, is the number of protons plus the number of neutrons in a nuclide. 20. Is the atomic or mass number listed on top in an equation? The mass number (A). 21. What is the mass number of a proton or neutron? 1. 22. Why is the mass number of an electron zero? (Hint – How big are electrons compared to protons and neutrons?) Electrons are significantly lighter than protons and neutrons, resulting in a mass number of 0. 23. What is the atomic number of an electron? -1. 24. On Slide #13, what does X represent? X is the parent nuclide. 25. On Slide #13, what does Y represent? Y is the daughter nuclide. 26. On Slide #13, what are the three types of radiation given off during radioactive decay? Alpha, Beta, or Gamma.

27. On Slide #14, how does the author describe a stable state being reached? Unstable nuclides that break down eject material in alpha, beta, or gamma radiation until they have reached a stable state where the nuclide is held together tightly. 28. What does an alpha particle consist of? Two protons and two neutrons. 29. What is the mass number and atomic number of an alpha particle? The mass number (A) is four, and the atomic number (Z) is two. 30. What happens to the parent nuclide when it loses an alpha particle? Since the parent nuclide loses an alpha particle, the daughter nuclide must be two protons and two neutrons smaller than its parent. Because of this, its mass number is reduced by four and its atomic number by two. 31. What object do you have in your house to safeguard you that releases alpha particles? Smoke detectors. 32. What is a beta particle? A beta particle is the ejection of a fast-moving electron from the nucleus of an unstable nuclide. 33. During beta decay, what happens to the atomic number? When a daughter nuclide is produced via beta decay, the effect is to raise the nuclide's atomic number by one while leaving the mass number unchanged. 34. What does a gamma-ray's emission do to the daughter nuclide's atomic and mass numbers? A gamma ray has extremely low mass and, therefore, has a mass number of zero and an atomic number of zero. 35. What does a gamma-ray's emission do to a nuclide's energy level? Gamma decay occurs when nuclides have too much energy. This can be from heating, absorbing light, or perhaps left over from a previous decay process. The nuclide releases a high-energy photon, a gamma ray, to release this energy. 36. How does LAX use gamma rays? Airport security uses them to look inside our luggage. 37. What is a decay series? A decay series is when a single nuclide undergoes several radioactive decay processes, one after the other, in a chain.

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38. What two things are being ejected from parent nuclides to make the daughter nuclides lighter and less energetic? As the decay chain progresses, more material and energy are ejected, making the daughter nuclides lighter and less energetic than their parents. 39. On Slide #18, which decay increases the atomic number by one? (Is it alpha or beta?) Beta. 40. On Slide #18, what does alpha decay do to the daughter nuclide’s atomic and mass numbers? The daughter nuclide experiences a decrease in atomic and mass numbers. 41. What is the half-life of a nuclide? The half-life of a nuclide is the length of time required for half of the nuclides in a sample to decay. 42. On Slide #19, if you begin with 16 yellow balls, how many balls remain after one half-life? 8. 43. On Slide #19, how many yellow balls remain after two half-lives have passed? 4. 44. On Slide #19, how many yellow balls would remain after four half-lives have passed? 2. 45. On Slide #21, what is the half-life of this imaginary element in years? Hint: See the x-axis at the bottom of the graph. Two years.

Radiometric Dating Q&A

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